Recent developments of the 3GPP Long Term Evolution (LTE) facilitate accessing local IP based services in the home, office, public hot spot or even outdoor environments. One of the important use cases for the local IP access and local connectivity involves the direct communication between wireless communication devices, e.g., user equipment devices (UEs), in close proximity (typically less than a few 10s of meters, but sometimes up to a few hundred meters) of each other. For example, when communication devices (referred to as devices for brevity) are proximately located to each other, they may be configured to operate in a device-to-device (D2D) communication mode in which they communicate through a link directly between them without routing of communications through any other device or radio network node (e.g., eNB). FIG. 1 illustrates a system in which a pair of electronic communication devices 100 and 102 (also referred to as communication devices and devices for brevity) can operate in a D2D mode communicating through a link directly between them, or alternatively can operate to indirectly communicate with each other through a radio network node 110.
This direct mode or device-to-device (i.e. D2D) communications enables a number of potential improvements over the relay of communications through a radio network node (e.g., cellular network), because the pathway between D2D devices can be much shorter than between indirect communication devices (e.g., cellular devices) that communicate via radio network node (e.g., cellular base station, eNB). The advantages of D2D communications may include one or more of the following:                Capacity gain: Radio resources (e.g. OFDM resource blocks) between the D2D and cellular layers can be reused (providing reuse gain). Moreover, a D2D link uses a single hop between the transmitter and receiver devices as opposed to the 2-hop link via a cellular radio network node, e.g., access point (providing hop gain).        Peak rate gain: Due to the proximity and potentially favorable propagation conditions higher peak rates can be achieved (proximity gain); and        Latency gain: When the devices communicate over a direct link, radio network node (e.g., eNB) forwarding is avoided and the end-to-end latency can decrease.        
Some appealing applications of D2D communications are video streaming, online gaming, media downloading, peer-to-peer (P2P), file sharing, etc.
In RAN1#76 Chairman's notes, February 2014, the following processes have been disclosed for scheduling assignments (SAs). For D2D broadcast communication, scheduling assignments that at least indicate the location of the resource(s) for reception of the associated physical channel that carries D2D data are transmitted by the broadcasting device, which is also referred to as a user equipment (UE). The indication of resource(s) for reception may be implicit and/or explicit based on scheduling assignment resource or content. In other words, SAs are used for D2D broadcast communication to at least indicate time resources when the corresponding D2D data are transmitted. The SA benefits and the related procedures have been described in R1-140778 entitled “On scheduling procedure for D2D”, Ericsson, February 2014.
Since SA is used to indicate the resource location to receiver devices, one aspect here is the resource pattern (RPT) design, i.e., location of subframes in which the D2D broadcast data transmissions will take place. The RPT design needs to consider the performance target, for example it is defined that the received power reference level should be larger than −107 dBm. To reach the −107 dBm power level, the following process may occur:                1) The occupied bandwidth is limited, to avoid collision in frequency domain.        2) The device (e.g., UE) hardware performance of in-band emission should be taken into account, to evaluate the adjacent-channel interference.        3) To compensate for bad channel quality (including high path loss, fading, co-channel interference, and/or adjacent channel interference), some L1 enhancement like re-transmission may be needed;        4) Re-transmission further increases the necessary resources for D2D transmission in time domain, which is more challenging for a TDD system where there are less UL sub-frames than a FDD system.        
D2D can be transmitted in uplink (UL) resources (UL subframe in a Time Division Duplex (TDD) system and UL band in a Frequency Division Duplex (FDD) system). Because of half duplexing, the device (e.g., UE) cannot transmit and receive at the same time. Half duplexing is also a factor which should be considered in RPT design.
In R1-141384, entitled “D2D Physical Channels Design”, Ericsson, April 2014, it has been proposed that the resource pattern design for a FDD system be as explained below and illustrated in FIG. 2, where the voice-over-IP (VoIP) traffic is considered. In FIG. 2 the y-axis (vertical axis) represents frequency domain and the x-axis (horizontal axis) represents time domain. UE-A (e.g., 100) transmits a scheduling assignment SA 200a on one frequency to UE-B (e.g., 102) and latter retransmits the scheduling assignment SA 200b on another frequency to UE-B to define a first data pattern at which voice packets 204 will be transmitted with hopping between two different frequencies. Similarly, UE-B (e.g., 102) transmits a scheduling assignment SA 202a to UE-A (e.g., 100) to define a second data pattern at which voice packets 206 will be transmitted with hopping between the two different frequencies.
In the example of FIG. 2, there is one voice packet created every 20 ms from an application layer, for which:                1) One SA pool is allocated, which allows one to four SA transmissions per 160 ms—SA cycle, i.e., to control the resource location for eight voice packets to be transmitted following the SA cycle;        2) Four data (re-)transmission per 20 ms are allocated, where 2RB bandwidth is allocated per data transmission; and        3) Between SA cycle and data transmission periods, i.e., during data transmission period, there are some subframes reserved for SA which are used for scheduling data packet in the following subframes.Potential Problems with these Approaches:        
Since the RPT design described in R1-141384 is for a FDD system and for VoIP traffic, it is hard to apply to a TDD system. For example, it requires at least 4 (for SA)+8*4 (for data)=36 for D2D broadcast transmission per 160 ms, which causes about 22.5% of resources to be allocated to D2D resources and may result in at least 22.5% UL throughput degradation of a cellular system. While for a TDD system, the available UL subframe number is between 10% (configuration 5) to 60% (configuration 0), which means in a TDD system, if reusing RPT processes from a FDD system, it would cause either larger UL performance degradation or result in not enough remaining resources even only for D2D broadcast communication.
One possible solution is to define many patterns, some optimized for FDD, some optimized for TDD, and all these different patterns are indicated via different indexes included in SA. However, SA payload must be minimized to provide an acceptable link budget, which is even more challenging in a TDD system with less UL subframes than a FDD system. Moreover for different traffic services the data pattern could be different because of different performance requirements.
Considering different traffic services and different TDD configuration scenarios, there could be a large number of data patterns. Then the number of pattern indexes would be too big and thus the pattern index length would be too large to be included in the limited SA payload.
The approaches described in the Background section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in the Background section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in the Background section.